The three-axis tracking structure of vehicular opto-electronic equipment with a latitude axis range of ±20° can not track all secondary planets in the half-airspace.So,this paper explores the principle of satellitic tracking,derives the relationship formulas between three axes and gives a tracking tactic arithmetic for the STTA satellite by a simulation.When a secondary planet with a tracking elevation above 70° is tracked,the azimuth-position horizon tracking mode is adopted.It not only uses the superiority of the horizon gimbal mode with a lower tracking error,but also conquers the altazimuth gimbal with tracking dead zone.When a secondary planet with a tracking elevation bellow 70°is tracked,the azimuth gimbal and following up mode is adopted.It combines the superiority of the horizon gimbal and altazimuth gimbal and receives the better effect.This arithmetic not only has solved three-axis turntable vehicular space but also has ensured the secondary planet in an assuring range and can capture all secondary planets in the half-airspace.The experimentation is designed,which verifies that the tracking tactic arithmetic is effective and feasible.